"In D&D rules, weight is measured in coins (cn) rather than pounds."
Yes, item weights are listed as coins. A chain mail armour weighs the same as 400 coins.
It then goes on to give four encumbrance levels:
*400 coins or less AND unarmoured
*401-600 coins OR leather armoured
*601-800 coins OR metal armoured
*801-1600 coins OR metal armoured and carrying treasure
In case of armour AND treasure you use a lower entry than you usually would. At the highest level your maximum move per round is 30' (you can't run). First of all, I think this is extremely simple and very much in line with the rest of the game. Yeah, you might complain that Strength is not taken into consideration but back then, Abilities had few real uses besides checks.
Second of all, I think it raises some serious implications. A fighter needs 2000 XP to reach lvl 2, I don't have the Expert book at hand, but it takes much much more than that to reach, say, level 5. Which means many, many hauls of treasure if you consider the old "treasure gained = XP gained" formula. Sure, you might find some golden candlesticks that weigh just 20 gp but are worth several hundred, but that's still far away from your goal. And carrying capacity doesn't increase with level, unlike the assumption I'm used to from 3E that monsters give more and more XP as you level up, keeping the progression nicely timed. In Moldvay, a level 6 monster gives just 275 XP, 500 if it has special abilities.
It made deciding what treasure to take and when to take that much more interesting. Also, when having a full plate means you are automatically fully encumbered when carrying treasure it means that even when the character find a huge amount of loot, they will have to go back for it many times, providing an outlet for adventure.
Ok, yeah, there's still the XP for defeating monsters, but it's usually almost neglectable (frex, the book give an example of the party gaining 5800 XP from treasure and 800 XP from monsters). It shows why killing the monsters wasn't really the focus. It was about looting the dungeon and being clever in the process, avoiding dangers and defeating foes with wits more often than with violence (which could easily get you killed).
Another interesting thing to note is that I couldn't find any equipment other than armour, weapons and magic items in the Basic book. Maybe I'm blind, but no ropes, 10 ft. poles or crowbars. That sucks, but I guess they're in there somewhere, maybe in the Expert book.